Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 04 May 2021

Evaluation of Fracture Resistance of Zirconia Modification/Polishing Around Implant Abutments

DDS, FACP,
MS, DDS,
DDS,
DDS, Dr Med Dent,
PhD, MPH,
DDS, FACP, and
DDS, FACP
Page Range: 202 – 209
DOI: 10.1563/aaid-joi-D-20-00144
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Subcrestal placement of implants may have interproximal bone proximity issues that interfere with the submucosal contour of implant-supported zirconia restorations during delivery of the restorations. Modification of the mesial distal submucosal areas may be necessary to fully seat the restoration without impingement of the interproximal bone. Our aim was to determine if modification of submucosal cervical contour of implant supported zirconia-titanium base (Zi-Ti base) restorations resulted in a significant change in fracture strength compared with Zi-Ti base restorations without any modification near the cervical submucosal area. Implant Zi-Ti base restorations designed in the form of a maxillary premolar were made for the Straumann implant lab analog. Zirconia samples were cemented onto the Ti-base and the test group (N = 20) underwent recontouring and polishing at the junction of the Zi-Ti base cervical areas. The control group (N = 20) did not undergo any modifications. All 40 samples underwent fracture testing with an Instron machine. We assessed differences between modified and unmodified implants restorations using a 2-tailed t test for independent samples. Fracture strength values (N) ranged from 4354.68 to 6412.49 in the test group (N = 20) and from 5400.31 to 6953.22 in the control group (N = 20). The average fracture strength in the control group (6154.84 ± 320.50) was higher than in the modified group (5593.13 ± 486.51; P < .001). Modification of submucosal contour significantly decreased fracture strength. However, the average fracture strength exceeded the masticatory forces of humans.

Figure 1.
Figure 1.

Impression coping radiograph of #23 and #26 implants placed subcrestal.


Figures 2 and 3.
Figures 2 and 3.

Figure 2. Occlusal view of implant supported tooth #5 design from CEREC 4.5.2.

Figure 3. Final premolar tooth #5 specimen designed on CEREC 4.5.2.


Figures 4 and 5.
Figures 4 and 5.

Figure 4. Unmodified zirconia specimen cemented onto Variobase and seated onto lab analog.

Figure 5. Modified mesial distal contours of specimen.


Figure 6.
Figure 6.

Occlusal loading onto zirconia specimen on Instron machine.


Figure 7.
Figure 7.

Boxplot of fracture strength values.


Figure 8.
Figure 8.

Mode of fracture of implant supported screw retained zirconia.


Figure 9.
Figure 9.

Specimen thickness from top of the Variobase to the occlusal screw access, 6 mm, measured on CEREC software.


Figures 10–13.
Figures 10–13.

Figure 10. Number 30 implant, impression coping radiograph of subcrestal placed implant.

Figure 11. Line drawing diagram of proposed various options for submucosal contour recommended to be included in laboratory prescription for implant supported restorations.

Figure 12. Clinical example of implant supported #30 crown before contour modification. Figure 13. Clinical example of implant supported #30 crown after contour modification.


Contributor Notes

Corresponding author, e-mail: jongheep@usc.edu
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